Allow user to specify the IP address epmd binds to

The IP address(es) epmd binds to can now be specified by the user,
either via epmd's new "-address" option or (if that's not used) by
setting the environment variable ERL_EPMD_ADDRESS. Multiple addresses
may be specified using a comma-separated list. If the loopback address
is not in this list, it will be added implicitly, so that the daemon can
be queried by an interactive epmd process.

erts/configure.in

@@ -1716,7 +1716,7 @@ AC_CHECK_FUNCS([getnameinfo getipnodebyname getipnodebyaddr gethostbyname2])
 
 AC_CHECK_FUNCS([ieee_handler fpsetmask finite isnan isinf res_gethostbyname dlopen \
 		pread pwrite writev memmove strerror strerror_r strncasecmp \
-		gethrtime localtime_r gmtime_r mmap mremap memcpy mallopt \
+		gethrtime localtime_r gmtime_r inet_pton mmap mremap memcpy mallopt \
 		sbrk _sbrk __sbrk brk _brk __brk \
 		flockfile fstat strlcpy strlcat setsid posix2time setlocale nl_langinfo poll])
 

erts/doc/src/epmd.xml

@@ -116,6 +116,16 @@
 
     <p>These options are available when starting the actual name server. The name server is normally started automatically by the <c>erl</c> command (if not already available), but it can also be started at i.e. system start-up.</p>
     <taglist>
+    <tag><c><![CDATA[-address List]]></c></tag>
+    <item>
+    <p>Let this instance of <c>epmd</c> listen only on the
+      comma-separated list of IP addresses and on the loopback address
+      (which is implicitely added to the list if it has not been
+      specified). This can also be set using the
+      <c><![CDATA[ERL_EPMD_ADDRESS]]></c> environment variable, see the
+      section <seealso marker="#environment_variables">Environment
+      variables</seealso> below.</p>
+    </item>
     <tag><c><![CDATA[-port No]]></c></tag>
     <item>
       <p>Let this instance of epmd listen to another TCP port than
@@ -228,6 +238,15 @@
     <marker id="environment_variables"></marker>
     <title>Environment variables</title>
     <taglist>
+      <tag><c><![CDATA[ERL_EPMD_ADDRESS]]></c></tag>
+      <item>
+        <p>This environment variable may be set to a comma-separated
+          list of IP addresses, in which case the <c>epmd</c> daemon
+          will listen only on the specified address(es) and on the
+          loopback address (which is implicitely added to the list if it
+          has not been specified). The default behaviour is to listen on
+          all available IP addresses.</p>
+      </item>
       <tag><c><![CDATA[ERL_EPMD_PORT]]></c></tag>
       <item>
         <p>This environment variable can contain the port number epmd will use.

erts/doc/src/erl.xml

@@ -981,6 +981,15 @@
 	  add to the code path.
   	  See <seealso marker="kernel:code">code(3)</seealso>.</p>
       </item>
+      <tag><c><![CDATA[ERL_EPMD_ADDRESS]]></c></tag>
+      <item>
+        <p>This environment variable may be set to a comma-separated
+          list of IP addresses, in which case the
+          <seealso marker="epmd">epmd</seealso> daemon
+          will listen only on the specified address(es) and on the
+          loopback address (which is implicitely added to the list if it
+          has not been specified).</p>
+      </item>
       <tag><c><![CDATA[ERL_EPMD_PORT]]></c></tag>
       <item>
         <p>This environment variable can contain the port number to use when

erts/epmd/src/epmd.c

@@ -33,6 +33,7 @@
 
 static void usage(EpmdVars *);
 static void run_daemon(EpmdVars*);
+static char* get_addresses(void);
 static int get_port_no(void);
 static int check_relaxed(void);
 #ifdef __WIN32__
@@ -133,6 +134,7 @@ int main(int argc, char** argv)
 {
     EpmdVars g_empd_vars;
     EpmdVars *g = &g_empd_vars;
+    int i;
 #ifdef __WIN32__
     WORD wVersionRequested;
     WSADATA wsaData;
@@ -158,8 +160,9 @@ int main(int argc, char** argv)
     g->argv = NULL;
 #endif
 
-    g->port  = get_port_no();
-    g->debug = 0;
+    g->addresses      = get_addresses();
+    g->port           = get_port_no();
+    g->debug          = 0;
 
     g->silent         = 0; 
     g->is_daemon      = 0;
@@ -168,12 +171,14 @@ int main(int argc, char** argv)
     g->delay_accept   = 0;
     g->delay_write    = 0;
     g->progname       = argv[0];
-    g->listenfd       = -1;
     g->conn           = NULL;
     g->nodes.reg = g->nodes.unreg = g->nodes.unreg_tail = NULL;
     g->nodes.unreg_count = 0;
     g->active_conn    = 0;
 
+    for (i = 0; i < MAX_LISTEN_SOCKETS; i++)
+	g->listenfd[i] = -1;
+
     argc--;
     argv++;
     while (argc > 0) {
@@ -208,6 +213,11 @@ int main(int argc, char** argv)
 	    else
 		usage(g);
 	    epmd_cleanup_exit(g,0);
+	} else if (strcmp(argv[0], "-address") == 0) {
+	    if (argc == 1)
+	      usage(g);
+	    g->addresses = argv[1];
+	    argv += 2; argc -= 2;
 	} else if (strcmp(argv[0], "-port") == 0) {
 	    if ((argc == 1) ||
 		((g->port = atoi(argv[1])) == 0))
@@ -252,13 +262,10 @@ int main(int argc, char** argv)
     /*
      * max_conn must not be greater than FD_SETSIZE.
      * (at least QNX crashes)
-     *
-     * More correctly, it must be FD_SETSIZE - 1, beacuse the
-     * listen FD is stored outside the connection array.
      */
 
     if (g->max_conn > FD_SETSIZE) {
-      g->max_conn = FD_SETSIZE - 1;
+      g->max_conn = FD_SETSIZE;
     }
 
     if (g->is_daemon)  {
@@ -393,11 +400,14 @@ static void run_daemon(EpmdVars *g)
 
 static void usage(EpmdVars *g)
 {
-    fprintf(stderr, "usage: epmd [-d|-debug] [DbgExtra...] [-port No] [-daemon]\n");
-    fprintf(stderr, "            [-relaxed_command_check]\n");
+    fprintf(stderr, "usage: epmd [-d|-debug] [DbgExtra...] [-address List]\n");
+    fprintf(stderr, "            [-port No] [-daemon] [-relaxed_command_check]\n");
     fprintf(stderr, "       epmd [-d|-debug] [-port No] [-names|-kill|-stop name]\n\n");
     fprintf(stderr, "See the Erlang epmd manual page for info about the usage.\n\n");
     fprintf(stderr, "Regular options\n");
+    fprintf(stderr, "    -address List\n");
+    fprintf(stderr, "        Let epmd listen only on the comma-separated list of IP\n");
+    fprintf(stderr, "        addresses (and on the loopback interface).\n");
     fprintf(stderr, "    -port No\n");
     fprintf(stderr, "        Let epmd listen to another port than default %d\n",
 	    EPMD_PORT_NO);
@@ -555,8 +565,9 @@ void epmd_cleanup_exit(EpmdVars *g, int exitval)
 	      epmd_conn_close(g,&g->conn[i]);
       free(g->conn);
   }
-  if(g->listenfd >= 0)
-      close(g->listenfd);
+  for(i=0; i < MAX_LISTEN_SOCKETS; i++)
+      if(g->listenfd[i] >= 0)
+          close(g->listenfd[i]);
   free_all_nodes(g);
   if(g->argv){
       for(i=0; g->argv[i] != NULL; ++i)
@@ -568,6 +579,10 @@ void epmd_cleanup_exit(EpmdVars *g, int exitval)
   exit(exitval);
 }
 
+static char* get_addresses(void)
+{
+    return getenv("ERL_EPMD_ADDRESS");
+}
 static int get_port_no(void)
 {
     char* port_str = getenv("ERL_EPMD_PORT");

erts/epmd/src/epmd_cli.c

@@ -137,7 +137,7 @@ static int conn_to_epmd(EpmdVars *g)
 
     { /* store port number in unsigned short */
       unsigned short sport = g->port;
-      SET_ADDR_LOOPBACK(address, FAMILY, sport);
+      SET_ADDR(address, EPMD_ADDR_LOOPBACK, sport);
     }
 
     if (connect(connect_sock, (struct sockaddr*)&address, sizeof address) < 0) 

erts/epmd/src/epmd_int.h

@@ -168,42 +168,40 @@
 #if defined(HAVE_IN6) && defined(AF_INET6) && defined(EPMD6)
 
 #define EPMD_SOCKADDR_IN sockaddr_in6
-#define FAMILY      AF_INET6
-
-#define SET_ADDR_LOOPBACK(addr, af, port) do { \
-    memset((char*)&(addr), 0, sizeof(addr)); \
-    (addr).sin6_family = (af); \
-    (addr).sin6_flowinfo = 0; \
-    (addr).sin6_addr = in6addr_loopback; \
-    (addr).sin6_port = htons(port); \
+#define EPMD_IN_ADDR in6_addr
+#define EPMD_S_ADDR s6_addr
+#define EPMD_ADDR_LOOPBACK in6addr_loopback.s6_addr
+#define EPMD_ADDR_ANY in6addr_any.s6_addr
+#define FAMILY AF_INET6
+
+#define SET_ADDR(dst, addr, port) do { \
+    memset((char*)&(dst), 0, sizeof(dst)); \
+    memcpy((char*)&(dst).sin6_addr.s6_addr, (char*)&(addr), 16); \
+    (dst).sin6_family = AF_INET6; \
+    (dst).sin6_flowinfo = 0; \
+    (dst).sin6_port = htons(port); \
  } while(0)
 
-#define SET_ADDR_ANY(addr, af, port) do { \
-    memset((char*)&(addr), 0, sizeof(addr)); \
-    (addr).sin6_family = (af); \
-    (addr).sin6_flowinfo = 0; \
-    (addr).sin6_addr = in6addr_any; \
-    (addr).sin6_port = htons(port); \
- } while(0)
+#define IS_ADDR_LOOPBACK(addr) \
+    (memcmp((addr).s6_addr, in6addr_loopback.s6_addr, 16) == 0)
 
 #else /* Not IP v6 */
 
 #define EPMD_SOCKADDR_IN sockaddr_in
-#define FAMILY      AF_INET
-
-#define SET_ADDR_LOOPBACK(addr, af, port) do { \
-    memset((char*)&(addr), 0, sizeof(addr)); \
-    (addr).sin_family = (af); \
-    (addr).sin_addr.s_addr = htonl(INADDR_LOOPBACK); \
-    (addr).sin_port = htons(port); \
+#define EPMD_IN_ADDR in_addr
+#define EPMD_S_ADDR s_addr
+#define EPMD_ADDR_LOOPBACK htonl(INADDR_LOOPBACK)
+#define EPMD_ADDR_ANY htonl(INADDR_ANY)
+#define FAMILY AF_INET
+
+#define SET_ADDR(dst, addr, port) do { \
+    memset((char*)&(dst), 0, sizeof(dst)); \
+    (dst).sin_family = AF_INET; \
+    (dst).sin_addr.s_addr = (addr); \
+    (dst).sin_port = htons(port); \
  } while(0)
 
-#define SET_ADDR_ANY(addr, af, port) do { \
-    memset((char*)&(addr), 0, sizeof(addr)); \
-    (addr).sin_family = (af); \
-    (addr).sin_addr.s_addr = htonl(INADDR_ANY); \
-    (addr).sin_port = htons(port); \
- } while(0)
+#define IS_ADDR_LOOPBACK(addr) ((addr).s_addr == htonl(INADDR_LOOPBACK))
 
 #endif /* Not IP v6 */
 
@@ -231,6 +229,8 @@
 /* Maximum length of a node name == atom name */
 #define MAXSYMLEN 255
 
+#define MAX_LISTEN_SOCKETS 16
+
 #define INBUF_SIZE 1024
 #define OUTBUF_SIZE 1024
 
@@ -299,7 +299,8 @@ typedef struct {
   Connection *conn;
   Nodes nodes;
   fd_set orig_read_mask;
-  int listenfd;
+  int listenfd[MAX_LISTEN_SOCKETS];
+  char *addresses;
   char **argv;
 } EpmdVars;